1.1V reference voltage (Nano)

[Coding_Badly]

v3xX:
Connecting a MQ-2 Sensor (+5V-GND) the voltage drops to 4005mV on the oscilloscope but the reference on the Arduino shows 4630mV.

This is the moment you scribble a schematic on a sheet of paper, take a reasonably good quality picture of that schematic, then post the picture.

v3xX:
that it is possible to measure the external voltage using the internal reference (1.1V for Nano).

It is...

Measurement of Bandgap voltage

I was surfing the postings on AVRfreaks site and came across an interesting topic where someone asked how and if they could measure the battery voltage that was powering their AVR chip. There were the normal suggestions of using a voltage divider across the battery and changing the A/D reference to the internal 1.1 band gap option. But also mentioned was a way I hadn't heard of or had known about before. It seems with the proper analog mux channel selection made, one can directly measure the 1…

https://forum.arduino.cc/index.php?topic=38119.0